In recent years, research and development has been conducted in the field of service robots which work in an environment containing a person. The service robots include, for example, a load-carrying robot which carries loads as a substitute for a person, a guard robot which conducts patrols of a facility, and a cleaning robot. These kinds of working mobile robots encounter a person while the robots are traveling. In that event, it is required for the robots to safely pass by the person.
As a conventional art, a technology of generating a trajectory of a robot to avoid a moving object typified by a human being (“On-line Motion Planning of an Autonomous Mobile Robot to Avoid Multiple Moving Obstacles Based on the Prediction of Their Future Trajectories” by Akira Inoue, Kenji Inoue, and Yoshikuni Ohkawa, Journal of the Robotics Society of Japan, 15 (2), pp. 249-260, Mar. 15, 1997) (Non-Patent Literature 1) This conventional art adopts a system of generating a trajectory to avoid multiple persons by predicting moving paths of the persons based on an idea using the potential method, which estimates that a person receives a virtual repulsive force of a robot which is approaching the person and, while changing the travel direction to a direction modified by the virtual repulsive force, moves in the modified direction.
The conventional art will be described in detail. FIGS. 34A and 34B schematically illustrate the conventional art. FIG. 34A illustrates initial positions of a robot R and two moving objects (persons) O1 and O2 with their directions of travel intersecting with one another. FIG. 34B illustrates a case where the robot R turns left while traveling. The moving object O2 accordingly changes its direction in order to move forward by avoiding the approaching robot R.
On that occasion, the robot R applies repulsive force to the moving objects (persons) O1 and O2 to predict the future moving paths of the moving objects (persons) O1 and O2 on the assumption that the robot R has a potential. As illustrated in FIG. 35, the direction of the resultant vector F of the attractive force Fni toward a goal of the objects O1 and O2 and the repulsive force Frij from the robot R of the moving object O1 or O2 is predicted as the paths of the moving objects O1 and O2. Based on the prediction, the robot R decides the action to take by itself (see Non-Patent Literature 1).